Patent Literature (PTL) 1 discloses a storage sub-system which is configured to minimize the degradation of system performance while improving reliability and availability of the storage sub-system. Specifically, the storage sub-system includes a first controller to control a plurality of drive units coupled to the first controller through a plurality of first switch devices, a second controller to control the a plurality of drive units coupled to the second controller through a plurality of second switch devices corresponding to the a plurality of first switch devices, and a connection path through which each of the plurality of first switch devices and the corresponding one of the plurality of second switch devices are coupled to each other. When the storage sub-system detects an occurrence of a failure, a defective portion in the connection path is identified and a coupling configuration of the switch devices is changed so as to avoid the defective portion.
Patent Literature (PTL) 2 discloses a data storage system in which controllers are coupled to a group of disk drives through transmission paths. The data storage system is configured to be capable of identifying which one of the group of the disk drives and the transmission paths has a failure when a failure is detected. Specifically, the data storage system includes a plurality of disk storage devices storing data and at least one pair of controllers which are coupled to the plurality of disk storage devices through one pair of transmission paths, respectively, and control accesses to the disk storage devices in response to access instructions from a higher-level device. In the data storage system, when one controller accesses a disk storage device through one transmission path, and detects an error from a result of the response from the disk storage devices, diagnosis processing is started in response to the detection. Then, the other controller is caused to access the disk storage device, which has been accessed by the one controller, through the other transmission path. From the result of the response from the disk storage device received by the other controller, either of the disk storage devices or the transmission path is identified to be the portion having a failure.